The present invention relates to lubricated copper or copper alloy sheet, strip, or foil of significantly improved working and forming properties, imparted by a novel lubricant-retentive, invisible surface coating, and to the method of manufacture thereof.
The mass production of small parts and articles of copper and copper alloys by individual or successive working and/or forming operations has long been known to require, among other items, the selection of the proper lubricant in order to prolong tool life and also to attain the desired unmarred surface appearance of the finished article. However, specialized lubricant compositions have at times been required in order to facilitate the working and forming operations, by effecting a sizeable reduction in friction. Quite often, these compositions must be removed from the work piece promptly after the operation, in order to avoid undesired tarnishing or harmful corrosion effects.
Thus, need has arisen for simplification of the manufacturing procedures by elimination of the need for specialized lubricant compositions and the requirement for prompt and frequent cleaning operations.
Some process steps in accordance with this invention may be carried out generally as described in U.S. Pat. No. 3,837,929 issued Sept. 24, 1974 and in related patents such as U.S. Pat. No. 3,677,828 issued July 18, 1972. Reference is likewise made to U.S. Pat. No. 3,224,908 issued Dec. 21, 1965 to Duch et al., as being the closest known prior art approach, though quite distant, in disclosing the coating of steel, to prevent corrosion and to provide good adherence of lacquers and varnishes, by treatment with a solution containing an alkene phosphonic acid, such as vinyl phosphonic acid, together with any of several varieties of polymers and copolymers.
It is therefore a principal object of this invention to provide a cupreous sheet, which term is intended to embrace sheet, strip, foil, or other article made of copper or of copper alloys, having a surface coating capable of strongly retaining, as by adsorption, a lubricant film which facilitates subsequent working or forming operations.
It is a further object to provide such coated cupreous sheet having an outer lubricant film retained thereon which in working or forming operations can effect a substantially greater reduction in frictional forces, and thus accomplish a far greater increase in lubricity, than the identical lubricant when applied directly to the uncoated cupreous sheet.
A further object is to provide a process which will efficiently and inexpensively provide a cupreous sheet with such a first surface coating and an outer lubricant film thereover.
Other objects and advantages of this invention will become apparent hereinafter.